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Water flow in the planted aquarium?

jcastell

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If one were to be very technical, the filter's output flow could easily be considered a series of harmonics based on the rotational frequencies and the water pressure pulses each blade of the pump produces

in practical terms we don't even need to go there, viewing it as a uniform flow is much more appropriate. I don't think we should even be thinking of the flow as waves, more like uniform particles coming out. You are talking about super positioning and cancellation effects of waves, not required for our objectives. The scale of effect is way too small to be even appreciable, and with newer pumps (not on commercial canisters mind) that operate at much higher rpms this effects is basically nil and can be treated as totally linear.

Flow in the tank is non-linear in the sense that it is possible that the unit volume passes a given point multiple times before leaving the tank - where it later returns. This is clearly cyclic and therefore, a harmonic analogy is absolutely appropriate.

I'm more concerned about the fluid dynamical effects that are happening than anything to do with harmonics or resonance. The question one should ask is the obvious, if there was such a point where the flow goes around itself is it localising the water or is it a, how shall I say, temporary holding area where the water gets moved on anyway. If it is the latter, we wouldn't care (well maybe the fish would care!), if the former then that would imply that whatever gets trapped gets localised and hence will never move from there creating a "holding area".

I've looked at Amano's tanks and he does nothing fancy - he doesn't need to. There's nothing fancy in this apart from using common sense. But there is a fine dividing line between having good flow around the tank to create a constant spring cleaning effect or blasting the hell out of everything.

If your objective is to make sure that the water is being mixed well to give immediate dilution effect then relatively low flow can achieve this as long as you strategically place the outputs right (and this requires experimenting). If we are talking about creating enough flow so that detritus gets swept into the currents and ends up getting sucked up in inlets of the canister filter then that is a different proposition altogether.
 

ceg4048

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Well I don't think that we're suggesting anything fancy. All we're saying is to avoid incoherent and disruptive flow.
I can't address Amano's tanks because I don't know all the things that he and his team does and I don't know what problems arise or how they are solved. We do know what happens in our tanks though because we see the difficulties every day and we are aware of what techniques work and which are less effective. As tanks become larger the effects become more pronounced. As lighting becomes higher the penalties of poor flow, i.e poor nutrition and algae, also become even more pronounced.

As I mentioned, we're not necessarily dealing with resonance itself, but with the similar mechanism by which external forces, such as pump outputs, combine to either be destructive or constructive.
jcastell said:
...But there is a fine dividing line between having good flow around the tank to create a constant spring cleaning effect or blasting the hell out of everything.
No, it's not. Not only is the line not fine but it's enormously thick. First of all, we're not talking about simple spring cleaning. What we're trying to achieve is maximum contact between the leaves and CO2. Highly lit, gas injected tanks are notorious for their inability to keep CO2 in solution long enough to satisfy the requirements of many plants. Aquatic plants have a difficult time transporting this gas across the external cell membranes. Adequate flow reduces the thickness of the boundary layer allowing better absorption of the gas. The same goes for nutrient uptake where stagnant areas in the immediate vicinity of the leaf causes a localized depletion of the nutrient concentration. Under high lighting these issues become critical and result in deficiencies. High flow also helps to carry away the metabolic waste products ejected from the plant. Of course, if the flow is too high then this becomes counter productive and that's why we use the visual analogue of "leaves gently rocking in the wind". As plant mass increases there is much more blocking of flow so what may seem to be excessive when the tank is first planted soon becomes sub-par.

T. Barr has reported that sample measurements taken of Amano tanks reveal that the PAR values are actually low - much lower than most of our tanks. The Amano scapes are also often very open savannah type scapes and are always meticulously cleaned and groomed. This could easily explain why those tanks are not penalized due to lower flow rates.

jcastell said:
If your objective is to make sure that the water is being mixed well to give immediate dilution effect then relatively low flow can achieve this as long as you strategically place the outputs right (and this requires experimenting).
Yes, we know that. As stated in the preceding posts, we've found that the best strategy will normally be to avoid collision of flow streams by ensuring uniform flow direction combined with a high pump rating more or less consistent with the 10X rule.

Cheers,
 

jcastell

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my problem with wanting well mixed flows is that most canister filters don't accommodate it according to their usage literature. And Eheim 2217 is said to be used for tanks up to 600 litres!! With our ways of thinking this is way too optimistic.

I've looked at Amano's filters, he uses a very strong pump that has a much higher head than Eheim or any other manufacturer uses, this means as the filter clogs it doesn't lose that much flow rate.

What I'm trying to get at is that flow rate for it's own sake can be achieved with loads of in tank flow pumps that do nothing but encourage water flow. But where does that leave the canister filters used. For the sake of argument you could have just one Eheim 2217 and loads of flow pumps in the aquarium to achieve your objective, but that would not be the way I would want to go about things.

In the interests of this thread please answer the following:

1) Is the biological load just as much a function of the plants kept as it is of the fish in the aquarium too? Dead plants produce ammonia, so you want it dealt with biologically, having good mixing will allow for the dilution effect but this also needs to be backed up with sufficient biological filtration and sufficient contact time with the biological filtration. In the other thread mentioning about canister filters you said the throughput was a problem. I stated it was not, but another thought also occurred to me: it makes no sense to have a 2217 canister pumping 2000 litres per hour or more because the contact time with the biological colony is decreased. The larger the canister the higher the flow rate we can put through it, and Amano seems to use quite conservative flow rates for his canister filters given their size and it strikes me that he wants to increase contact time with the biological colony when the water gets through it.

2) what happens to the detritus that sinks and ends up in the gravel? Do we still have to clean it out or will it rot and break down of its own accord? Apart from going to extremes we are always going to get some that will end up in the gravel (depends on fish loads of course!). Is this one of the reasons why people get blue green algae in the front glass since it's been triggered by this?
 

ceg4048

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jcastell said:
my problem with wanting well mixed flows is that most canister filters don't accommodate it according to their usage literature. And Eheim 2217 is said to be used for tanks up to 600 litres!! With our ways of thinking this is way too optimistic.
Yes, Eheim are known for their optimistic flow ratings. In non-planted, low stocking level tanks this doesn't matter, especially when using high surface area media such as their generally overpriced sintered glass media (or competitors equivalent.) While detritus does build up, Eheim and others assume this will be taken care of via water change. As these generic tanks are also typically low light there is much more margin for error. Manufacturer's tank capacity filter ratings are therefore based solely on the ammonia pull-down ability to levels which would show zero on a consistent basis on an ammonia test kit (assuming a fully cycled tank).

jcastell said:
I've looked at Amano's filters, he uses a very strong pump that has a much higher head than Eheim or any other manufacturer uses, this means as the filter clogs it doesn't lose that much flow rate.

What I'm trying to get at is that flow rate for it's own sake can be achieved with loads of in tank flow pumps that do nothing but encourage water flow. But where does that leave the canister filters used. For the sake of argument you could have just one Eheim 2217 and loads of flow pumps in the aquarium to achieve your objective, but that would not be the way I would want to go about things.
Yes, many folks find that simply adding Koralias or other pumps will add flow and this, if distributed correctly will definitely achieve the objective of addressing the boundary layer issues, enabling better penetration of nutrients/CO2.

Filtration and Flow/Distribution are separate entities. Flow is as important as Filtration because it feeds the plants, so there is
value in adding more pumping, but there is an aesthetic penalty. After all, the fashionable trend is to remove equipment from the tank for a more natural look. Using a filter(s) that satisfy/exceed the 10X rule kills two birds with one stone and satisfies the aesthetic imperative.

jcastell said:
In the interests of this thread please answer the following:

1) Is the biological load just as much a function of the plants kept as it is of the fish in the aquarium too? Dead plants produce ammonia, so you want it dealt with biologically, having good mixing will allow for the dilution effect but this also needs to be backed up with sufficient biological filtration and sufficient contact time with the biological filtration. In the other thread mentioning about canister filters you said the throughput was a problem. I stated it was not, but another thought also occurred to me: it makes no sense to have a 2217 canister pumping 2000 litres per hour or more because the contact time with the biological colony is decreased. The larger the canister the higher the flow rate we can put through it, and Amano seems to use quite conservative flow rates for his canister filters given their size and it strikes me that he wants to increase contact time with the biological colony when the water gets through it.
Plants add to the bio-load, not just because of dead leaves, but because of the high metabolic rate induced by the high lighting and massive carbon (and other nutrient) consumption. This results in ejection of carbohydrates, lipids and proteins which incidentally, feeds the critters in the bio-film/filter. I'm guessing that this actually speeds the metabolic rate of the microbes which affects the ammonia production rate and levels. But there is plenty of space on the bio-media and the oxygenation which occurs as a direct result of plant photosynthesis also finds it's way to these critters thereby enhancing their populations. As long as there is plenty of bio-media and microbial population one need not worry too much about contact time of the water with an individual bacterium. This has never been an issue with high throughput filtration.

jcastell said:
2) what happens to the detritus that sinks and ends up in the gravel? Do we still have to clean it out or will it rot and break down of its own accord? Apart from going to extremes we are always going to get some that will end up in the gravel (depends on fish loads of course!). Is this one of the reasons why people get blue green algae in the front glass since it's been triggered by this?
Detritus not picked up by the filter rots in the sediment. The combination of this rotting and any external lighting does contrbute to the BGA seen at the sediment line. Running a length of black electrical tape along this line will cut the light and reduce the amount of BGA formation. Good flow distribution to the bottom also minimizes this problem.

The rotting is also precisely why it's not a good idea, in a high light tank, to disturb the sediment without then doing a water change to dilute the ammonia that has been kicked up. The result is often algal blooms. Those with a fully carpeted bottoms have little choice though, except when changing out carpet sections or re-scaping. This isn't too big of a deal as the ammonia in the sediment feeds the carpet plant roots.

Cheers,
 

plantbrain

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Let me stick a hot pepper in the mix.

What does a large water change do?

Think about it in terms of gas space, aerenchyma, and how much that can hold as far as O2/Co2, current, boundary layers etc.

If you did a large water change, say 7x a week, say after 1-2 hours after the lights came on, what might this do to the current/plant growth (if practical obviously)?

What about a good sized wave timer system?

Regards,
Tom Barr
 

jcastell

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this is just a guess since I'm an amateur, and you'll have to excuse me since I'm not a chemist so I'll have to make educated guesses and assumptions, which I'll gladly have corrected:

well a large water change will take out spores and drop the ammonia levels as stated, but is would also reset the nutrient levels, and I take it because of this there'll be more gas space since nutrients have taken it up as they don't do now? So O2 and CO2 are easier to inject after the water change? (Of course this depends on what kind of water you are changing it with and the assumptions about it!)

Would the plants get a little boost in CO2 uptake after a water change, I always notice pearling after a water change.

But you either have to be a complete masochist or have a very elaborate plumbing arrangement to be doing a water change every day!!

I can't see a good sized wave timer doing much on its own apart from encouraging more uniform mixing.

Out of interest Tom, what is the average size of an algae spore? Is it possible to remove them with a 50 micro mesh filter?
 

Norfolk180Rio

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Ceg, any problems with back flow of water towards the CO2 cylinder when the CO2 is off during the night when using the cal aqua inline diffuser? I know you can put a valve in but this would be effective enough when having 1200 or so liters of water passing through per hr?
 

ceg4048

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Hi,
It doesn't matter how many litres. It only matters what the relative pressures are. The pressures are a function of the relative distances from the water level of the tank. When you turn the gas off water will backflow down through the diffuser so you need a check valve to stop it. No big deal.

Cheers,
 

dw1305

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Hi all,
This is a good thread.
Adequate flow reduces the thickness of the boundary layer allowing better absorption of the gas. The same goes for nutrient uptake where stagnant areas in the immediate vicinity of the cause a localized depletion of the nutrient concentration.
&
Plants add to the bio-load, not just because of dead leaves, but because of the high metabolic rate induced by the high lighting and massive carbon (and other nutrient) consumption. This results in ejection of carbohydrates, lipids and proteins which incidentally, feeds the critters in the bio-film/filter. I'm guessing that this actually speeds the metabolic rate of the microbes which affects the ammonia production rate and levels. But there is plenty of space on the bio-media and the oxygenation which occurs as a direct result of plant photosynthesis also finds it's way to these critters thereby enhancing their populations. As long as there is plenty of bio-media and microbial population one need not worry too much about contact time of the water with an individual bacterium. This has never been an issue with high throughput filtration.
I've spent quite a long time playing about with these as part of my "day job". The important factors are the ones quoted above, that flow speed is the factor that regulates gas uptake, this applies to the gas exchange at the water surface as well. This is a "corals" link, but it gives some details http://www.advancedaquarist.com/2007/1/aafeature/
and the other factor is, oxygen levels in the biological filtration media often limit nitrification, this is one that is very relevant to those who keep fish with high oxygen demand (or have lots of CO2 because of the Bohr effect), particularly if they don't have plants in their systems, so the aquaculture industry as well as Plec and Hill-stream loach keepers. Nearly all the problems with biological filtration arise because the potential BOD exceeds the oxygen content of the system, rather than there being insufficient bacteria or sites for biofiltration.

I was asked to write on "aeration and oxygenation" for a plec keeping forum, the article is hosted at "Plecoplanet" at the moment, although I'm not sure you can access without being a member. http://plecoplanet.com/?page_id=829.

cheers Darrel
 

Harkle420

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what a awesome thread!! Have spend about a hour reading this!!! I have a 180 litre tank which i run just one fuval external and a eheim 2217, but i do not run the eheim, because it is loud! it needs a clean!! i am so cleaning it tomorrow! i was a bit worried blowing off all my co2 with to much surface movement!! but after reading this just going to put the output at half height!! any hints???!!!!
 

ceg4048

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dw1305 said:
I was asked to write on "aeration and oxygenation" for a plec keeping forum, the article is hosted at "Plecoplanet" at the moment, although I'm not sure you can access without being a member. http://plecoplanet.com/?page_id=829.
Yes! it lets you in even as a non-member (don't tell the Mods! :shh: ) Nice article Darrel. Excellent data for any fish and any tank, really.

Harkle420 said:
i was a bit worried blowing off all my co2 with to much surface movement!! but after reading this just going to put the output at half height!! any hints?
Actually, as long as you don't break the surface (i.e. no white water, foaming or bubbles) then you're OK. Try placing the output just below the surface.

Cheers,
 

Harkle420

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just clean my spinning thing, sorry can not spell improperrr, i am a idoit i mean dyslxia!! you know what i mean!! lol lo :lol: :lol: l!! put my outlet just below surface is working a treat!! Leaves blowing in the wind + all my plants are pearling!! lol
so sorry spelling on this and all my post!! :lol:
 

plantbrain

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dw1305 said:
Hi all,
This is a good thread.
Adequate flow reduces the thickness of the boundary layer allowing better absorption of the gas. The same goes for nutrient uptake where stagnant areas in the immediate vicinity of the cause a localized depletion of the nutrient concentration.
&
Plants add to the bio-load, not just because of dead leaves, but because of the high metabolic rate induced by the high lighting and massive carbon (and other nutrient) consumption. This results in ejection of carbohydrates, lipids and proteins which incidentally, feeds the critters in the bio-film/filter. I'm guessing that this actually speeds the metabolic rate of the microbes which affects the ammonia production rate and levels. But there is plenty of space on the bio-media and the oxygenation which occurs as a direct result of plant photosynthesis also finds it's way to these critters thereby enhancing their populations. As long as there is plenty of bio-media and microbial population one need not worry too much about contact time of the water with an individual bacterium. This has never been an issue with high throughput filtration.
I've spent quite a long time playing about with these as part of my "day job". The important factors are the ones quoted above, that flow speed is the factor that regulates gas uptake, this applies to the gas exchange at the water surface as well. This is a "corals" link, but it gives some details http://www.advancedaquarist.com/2007/1/aafeature/
and the other factor is, oxygen levels in the biological filtration media often limit nitrification, this is one that is very relevant to those who keep fish with high oxygen demand (or have lots of CO2 because of the Bohr effect), particularly if they don't have plants in their systems, so the aquaculture industry as well as Plec and Hill-stream loach keepers. Nearly all the problems with biological filtration arise because the potential BOD exceeds the oxygen content of the system, rather than there being insufficient bacteria or sites for biofiltration.

I was asked to write on "aeration and oxygenation" for a plec keeping forum, the article is hosted at "Plecoplanet" at the moment, although I'm not sure you can access without being a member. http://plecoplanet.com/?page_id=829.

cheers Darrel

Nice article Darrel, that's a goodie.
Post it here in the stickies, it's more than worthy.

I'm a pleco freak and have had many species, bred quite a few and many of my flow patterns in all my tanks are designed for their needs. Anyone with as many plecos as I have is got the disease.
They ARE definitely more sensitive to cO2 than most species, some are not bad, others are very touchy.

All the plant detirus added a lot to the BOD. And if the plants are hurting........a LOT more so.
Healthy plants contribute about 5-10% of their fixed carbon to the system as BOD.
A well groomed and pruned tank will have much less BOD and will likely be much healthier over the long term.

This export via water changes seems to be a large factor with the amplified CO2 enrichment methods, whereas with non CO2, the loading is reduced a great deal. That is speculation/a hypothesis though.

I have about 20-30X turnover per hour in all my tanks, and I have switched to wet/dry filters that are sealed to reduce CO2 loss, but still bump the O2 up 1-2ppm typically vs a canister filter over the 24 hour period. I also tend to have 2-4x the typical fish load, sometimes 100% more fish than some planted folk's tanks.

I also like to be able to feed the fish well.

A good method for measuring flow is from the reef side of things:
http://www.advancedaquarist.com/2011/7/ ... =clickthru

I want one :D
Really, I do.
 

dw1305

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Hi all,
I was asked to write on "aeration and oxygenation" for a plec keeping forum, the article is hosted at "Plecoplanet" at the moment, although I'm not sure you can access without being a member. http://plecoplanet.com/?page_id=829.........Nice article Darrel, that's a goodie. Post it here in the stickies, it's more than worthy.

Thanks, I'm away for a couple of weeks now, but I'll update the links and add it to UKAPS when I get back.

cheers Darrel
 

GillesF

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My plants are only gently moving at one specific spot in my tank. I assume this is poor circulation?

*edit* and another question: if you're using a spraybar, should it point directly to the front glass or somewhat downwards?
 

veryl

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19 Dec 2009
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Hydor has just put out a wave maker under 100.00 U.S.D. Fits my price range and their new koralia models are at least 3 times better than the old ones. Model 1400 gph is 5.5 watts and smaller models maybe 4 watts, wave maker will
handle 200 watts, this means i could run as many as 40 koralias off the one wave maker. Glad i didn't spend 425.00
on the one i wanted. Foster and Smith has this unit for $69.00 right now. Going to run a 750 on a 75 gal and a 90
gal tank a 1150 on a 125 and a 1400 is up and running on my 150 gal.
Having trouble deciding which way to point them, currently have it point down the lenght on 6ft tank.
will give my opion on them in couple weeks as 3 more arrive tomorrow.
 

peaches

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I hope you dont mind me adding to this thread, but it seems silly to start a new one asking similar questions. I am in the process of setting up this rather interesting shaped tank that I rescued for the princely sum of £10.

th_newtanku013.jpg

Its not quite finished (as you can see), but the height is almost 3ft, and the footprint 15 inches by 17 inches. I am planning a bit of emersed growth where possible, at the moment I have no CO2 and only low lighting 3 x 8 watt T5s, its a bit of an experiment I suppose. The installation of the Fluval 203 has given me a few headaches. It was originally going to be an eheim 2213 but I broke it!

Getting to the point, on such a tall tank is a spray bar best for water movement? I had a spray bar yesterday and the "management" complained about the noise from the water spoiling his TV viewing.
The spray bar was a couple of inches above the water line. Now I just have a plain open pipe until I decide what to put on the end of it. If I have a spray bar I would have to have it on or close to the waterline to prevent noise. However, this will spoil my emersed growth idea as I will need a bit of spray on the leaves of the anubias.

I am still working on the plants and waiting for my long planting tongs to come through the post, hence the poor arrangement of vallis. No fish yet, going to put some splash tetras and marble hatchets in. Any filter intake and output suggestions would be welcomed. thank you!
 

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